This change fixes SeatUnity to extend its parent class's create_session() and create_greeter_session() functions rather than override them.
This merge proposal is the same as the last proposal except:
* commits have been rebased onto latest lp:lightdm
* unwrapped long line based on review feedback
* new branch location
(lp:~ubuntu-multiseat/lightdm/seatunity-call-parent instead of
lp:~a7x/lightdm/seatunity-call-parent)
.
Approved by PS Jenkins bot, Robert Ancell.